I'm trying to make manipulateVariablesInPowermailAllMarker work to manipulate the values of an array field (e.g. checkbox, multiselect) in the {powermail_all} marker.

Let's assume my field my_checkboxes is defined like this and the user selects option 1 and 3.

Option One|1
Option Two|2
Option Three|3

And now I want to manipulate the selected options via TypoScript:

plugin.tx_powermail.settings.setup {
    manipulateVariablesInPowermailAllMarker {
        optinMail {
            my_checkboxes = TEXT
            my_checkboxes.field = value
        }
    }
}

Unfortunately this seems to have a bug: value is always the json notation of all selected options (e.g. ["1","3"]), i.e. in the mail the value is rendered as ["1","3"], ["1","3"]. Is there another property I oughta use to access the single option's value?

I think the problem roots in how ManipulateValueWithTypoScriptViewHelper.php ignores the correctly passed {subValue} from PowermailAll/Mail.html:

<f:for each="{answer.value}" as="subValue" iteration="index">
	<f:if condition="{subValue}">
		<vh:misc.manipulateValueWithTypoScript answer="{answer}" type="{type}">{subValue}</vh:misc.manipulateValueWithTypoScript><f:if condition="{index.isLast}"><f:else>, </f:else></f:if>
	</f:if>
</f:for>

    public function render(): string
    {
        $answer = $this->arguments['answer'];
        $type = $this->arguments['type'];
        $value = $this->renderChildren(); // this is subValue!
        if ($answer->getField()) {
            if (
                isset($this->typeToTsType[$type]) &&
                !empty($this->typoScriptContext[$this->typeToTsType[$type] . '.'][$answer->getField()->getMarker()])) {
                $this->contentObjectRenderer->start($answer->_getProperties());
                $value = $this->contentObjectRenderer->cObjGetSingle(
                    $this->typoScriptContext[$this->typeToTsType[$type] . '.'][$answer->getField()->getMarker()],
                    $this->typoScriptContext[$this->typeToTsType[$type] . '.'][$answer->getField()->getMarker() . '.']
                );
            }
        }
        return (string)$value;
    }

When changing $this->contentObjectRenderer->start($answer->_getProperties()); to $this->contentObjectRenderer->start(['value' => $value]); it's working fine.